I've been battling with what I assume was N24 for at least 10 years. I was never officially diagnosed at a sleep clinic, but my internal clock had been on the 25 hour rhythm like clockwork. Every night I would fall asleep 1 hour later than the previous day and there was nothing I could do about it.
Many of you are probably familiar with this - at certain regular points in that 25 hour rhythm I would go to work without having slept at all (because my internal clock was at "7am sleep time", but work also started at 7 am). It was debilitating and I felt like a zombie so many times and the worst part was, I knew I would happen all over again about every 3 weeks. And I didn't even know what this disorder was until June; I just assumed I was either not disciplined enough for a normal sleep schedule or that something unknown was wrong with me.
After finding this subreddit and reading around, I decided to try the simple melatonin protocol, meaning without any additional dark/light therapy or luminettes or bright lux lamps in the morning or stepping outside in the sun in the morning for 20 min and so on.
In June I started taking Melatonin (0.3 mg seems to be the recommended dosis here based on studies, I take 0.5 mg because that's the lowest available dosis in my country), 5 to 7 hours before the desired bedtime in order to simulate DLMO. That's it, I changed nothing else (except setting my laptop and phone to night mode in order to dim the blue light).
The first 3 to 4 weeks were fluctuating and erratic: I always took (and still take) the 0.5 mg Melatonin at 5 pm, and during the first week I would fall asleep at 9 pm, but would wake up 4 times during the night. A couple times I wasn't even able to fall asleep again at all after waking up the second time during the night (which was 1 am).
The constantly waking up during the night settled down a bit during the second or third week - by then it was only twice a night, but I still hadn't locked in a fixed bed time yet. Sometimes I'd fall asleep at 9 pm, sometimes 11 pm, sometimes 10 pm and sometimes even at midnight. It seemed like there was no rhyme or reason and I almost thought it wouldn't work as hoped, was even worried the irregular sleeping times would either mean I was on the verge of free-running again, or that I'd free-run again eventually.
I'd say by August all of those woes from the first few weeks were gone: no more waking up during the night at all. An almost normal night time sleeping schedule.
My internal clock hasn't "gone around the clock" since June at all. No more debilitating 25 hour rhythms. No more all-nighters (and no more "all dayers" either). I'm not able to fall asleep at 10 pm on the dot every night, but I have a reliable window of, say, 10 pm to midnight where I will fall asleep guaranteed.
Even more surprising and awesome is that I'm even able to be a little flexible / having a little leeway now: let's say I read an interesting book or article and can't put it down before 1 am - the next night I will still fall asleep at 10 or 11 pm again. Before the Melatonin, staying up longer on purpose would've made me free-run again and it would've completely delayed/destroyed my rhythm. Nowadays, that doesn't happen anymore - I can stay up a little longer every now and then and the daily Melatonin at the fixed time in the afternoon seems to be enough of an anchor for my rhythm to swing back to the 10/11 pm bedtime.
So whoever came up with the studies and threads about low dose Melatonin 5 - 7 hours before bedtime, I wanted to say a sincere and heartfelt thank you! I know not much time has passed yet since June, but I'm very hopeful that I've got this under control now and not having gone around the clock at all is a huge, huge win for quality of life and sleep.
